Variable condenser



y 28, 1929- w DUBILIER 1,714,662

VARIABLE CONDENSER Filed Sept. 16, 1922 IN VEN TOR By 3W,

A TTORNE Y5 Patented May 28, 1929.

UNITED STATES WILLIAM DUBILIER, or NEW yonx, N.

Y., ASSIGNOR TO DUBILIER CONDENSER CORPORATION, A. CORPORATION OF DELAWARE.

VARIABLE CONDENSER.

Application filed September 16, 1922. Serial No. 588,528.

This invention relates to variable electrical condensers and is directed more particularl to a condenser structure of the type in which the fixed and rotatable plates are in intimate frictional engagement as distinguished from .the type of variable condenser wherein the two sets of plates are separated by an air space.

In my copending application, Serial Number 576,235 filed July 20, 1922, there is described and claimed, a variable condenser in which the fixed plates each consist of a pair of thin mica discs with asheet of metal foil interposed therebetween, and in which the adjustable plates are of metal and alternately interleaved with the fixed plates and in frictional engagement therewith.

The present invention is closely related to that described in the above mentioned copending application and its object is the provision of a simple and economical condenser structure of the type referred to.

The preferred form of structure in accordance with this invention embodies a metal casing having in its interior one or more pairs of opposed surfaces constituting the fixed plates, and one or more rotatably adjustable plates, each comprising a pair of thin mica discs with a sheet of metal foil interposed therebetween. The rotatable plates are alternately interleaved with the fixed plates and the clearance between adjacent plates is preferably very slight-a close running fit being most desir-able.

The rotatable plate or plates are mounted on a shaft which is journaled in the casing, and the sheet or sheets of metal foil are, preferably, connected with the shaft or a suitable metallic member carried thereby.

When it is desired to provide more than one rotatable plate, it is preferable that. the metal casing be a die-casting having integrally cast parallel fixed plates so spaced that the rotatable plates will fit closely therebetween. The die-castings are relatively inexpensive when produced in sufficient quantities, but there are at times some slight irregularities in the fixed plates due to warping caused prob ably by uneven shrinkage of the metal coolmg. These slight irregularities in the fixed plates are, however, of little or no consequence in a condenser constructed in accordance with the present invention because of the fact that the rotatable plates are sufliciently resilient to readily yield to slight surface imperfections.

The invention will be better understood from the following detailed description with reference to the accompanying drawing in which Fig. 1 is aplan view of a rotatably adj ustable plate and its shaft;

Fig. 2 is a cross-sectional view taken along the line 22 of Fig. 1; I

Fig. 3 is a cross-sectional view of a condenser in accordance with this invention, having a single rotatable plate;

Fig. 4: is a plan view of the lower half of ihe metal casing taken along the line 44 of Fig. 5 is a plan view of the upper half of the casing of Fig. 3, viewed in the opposite direction to that of Fig. 4;

Fig. 6 is a cross-sectional view of a variable condenser having a plurality of rotatable plates and a die-cast casing; and

Fig. 7 is a plan view of the upper portion of th; casing of Fig. 6 as viewed from the under $1 e.

The rotatable plates 1, as is shown most clearly in Figs. 1 and 2, each comprise a pair of superposed mica discs 1*, 1 and an interposed semi-circular sheet of metal foil 1, having a thickness of a few thousandths of an inch. The mica discs are preferably secured togetherwith a suitable adhesive {thereby '85 completely enclosing the metal foil.

The shaft on which the disc 1 is mounted, as shown in F ig. 2, comprisesa shouldered cylindrical member 2 of insulating material such as hard rubber, a threaded metallic piv- ,90 0t member 3, and a nut 4. The pivot member 3 is threaded into the member 2, and the nut t is threaded into the pivot member 3.3 When thus assembled with the plate 1 in place, pins 5 are driven in to prevent plate 1 rotating rel; atively' to member 2. The metal foil is arranged to make contact with the pivot member 3 or with the nut 4.

The casing of Fig. 3

portion 6 and a comprises an upper lower portion 7, both of metal such as brass. The two portions are secured together with six flat head screws 8. When thus assembled, the two semi-circular parallel surfaces 6 and 7 are assembled by a distance just sufficient to permit of a running fit for the rotatable plate 1.

The lower end of the pivot member 3 is journaled in a step bearing 9 which is preferably of hard rubber or some other suitable insulating material.

In order to effect anoutside electrical connection with the metal foil 1 of the rotatable plate, a contact spring 10 having an aperture 10' for receiving the end of the pivot member 3, contacts with the under side of the nut 4 and is insulatively attached to the lower portion 7 of the casing by means of a round head screw 11 and nuts 12. The hard rubber bushing 13 and insulators 14, 15 separate the contact spring 10 and screw 11 from the metal casing. Circuit connections may be made to the screw 11 and the binding post 16, shown in Fig. 5the latter being metallically connected with the upper portion 6 of the casing.

A knob 17 is provided for rotating the plate 1 to effect capacity adjustments, and is attached to member 2 by means of set screw 18.

In the structure of Figs. 6 and 7 the upper portion 19 of the casing is, preferably, a metal die-casting and includes four integrally cast fixed plates 19*. The lower portion 20 of the casing may also be a die-casting, but, if preferred, it may be an ordinary sand moulded casting. The two portions of the casing are secured together by flat head screws 21. The spaces between the fixed plates 19 may, of course, be quite accurate in a die-cast product. and are gauged to provide a running fit for the rotatable plates 22. The latter, however, are quite resilient and therefore, permit some slight irregularities in the fixed plates without any excessive obstruction to their movement.

The rotatable plates 22 are spaced by the metal washers 23 and secured to the hard rubber member 24 by the pivot member 25 and pins 26. Members 24 and 25- to ether are referred to hereinafter as a shaft. 1 ember 24 is journaled in an aperture in the upper portion 19 of the casing, and the lower end of the pivot member 25 is journaled in the step bearing 27. A contact spring 28 corresponds wit contact spring 10 of Figs. 3 and 4. A knob 29 for turning the rotatable plates 22 is secured to the member 24 by the set screw 30.

I claim:

1. In a variable condenser, a metal casin defining a chamber having a pair of opposed parallel surfaces, a rotatable plate interposed between said surfaces, said rotatable plate comprising a pair of mica discs, a sheet of metallic foil interposed between said mica discs, and means for rotating said rotatable plate.

2. In a variable condenser, a metal casing defining a chamber having a pair of opposed parallel surfaces, a rotatable plate interposed between said surfaces, said rotatable plate comprising a pair of superposed mica discs and a sheet of metal foil interposed between said mica discs, said rotatable plate being in frictional enga ement with at least one of said surfaces, an means for rotating said rotatable plate.

3. In a variable condenser, a metal casing defining a chamber having a pair of opposed parallel surfaces, a rotatable plate interposed between said surfaces, said rotatable plate being in frictional engagement with at least one of said surfaces, said rotatable plate comprising a' pair of superposed mica discs and a sheet of metal foil interposed between said mica discs, a rotatable shaft to which said rotatable plate is secured, and a contact spring for effecting electrical connection with said metal foil.

4. In a variable condenser, a rotatable element comprising a shaft, a plate carried by said shaft comprising a pair of superposed mica discs and a sheet of metal foil interposed between said mica discs, said metal foil being electrically connected with a metallic portion of said shaft, and a conductor in frictional engagement with said metallic portion.

5. In a variable condenser, a metallic casing comprising a plurality of portions, at least one of said portions being a die-casting and including a plurality of integrally cast parallel plates, a shaft journaled in said casing, and a plurality of rotatable plates carried by said shaft and alternately interleaved with said first mentioned plates, said rotatable plates each comprising a pair of mica discs and a sheet of metal foil interposed between said mica discs.

6. In a variable condenser, a fixed electrode assembly comprising a. plurality of metallic surfaces, a rotatable plate operatively associated with said fixed electrode assemsaid rotatable plate comprising at least one mica sheet and a metallic sheet, said mica sheet being in frictional engagement with one of the metallic surfaces of said fixed electrode assembly and means for operating said rotatable plate.

7. In a variable condenser, a fixed electrode assembly having a plurality of metallic surfaces, a flexible, rotatable plate operatively associated with said fixed electrode assembly, said rotatable plate comprisingi'affpi'rr of mica discs and a sheet of metal interposed between said mica discs, and means for rotating said rotatable plate into frictional enpair of super-imposed mica discs, a. sheet of gagement with a plurality of the metallic metal foil interposed between said mica discs, 10 surfaces of the fixed electrode assembly. and means for rotating said plate into fric- 8. Ina variable condenser,afixed electrode tional engagement with a plurality of the member having a plurality of fiat metallic metal surfaces of the fixed electrode. surfaces, a flexible, rotatable plate oper- In testimony Where0f,Iafiix my signature. atively associated with said fixed electrode member, said rotatable plate comprising a WILLIAM DUBILIER. 

